Ignition system



Jan. 9, 1958 w. R. JOHNSON 3,362,389:

IGNITION SYSTEM Filed Dec. 1, 1965 INVENTOE WALlAfE B JOHNSON WM 4 flake/1'6 United States Patent 3,362,389 IGNITION SYSTEM Wallace R. Johnson, Mundelein, Ill., assignor to Outboard Marine Corporation, Waukegan, Ill., a corporation of Delaware Filed Dec. 1, 1965, Ser. No. 510,890 1 Claim. (Cl. 123148) ABSTRACT OF THE DISCLOSURE Disclosed herein is an ignition system including an arrangement for grounding the primary coil in the event of reverse rotation so as to prevent reverse rotation operation.

This invention relates to ignition systems and to methods of operating ignition systems and, more particularly, to ignition systems for internal combustion engines.

An object of the invention is to provide an ignition system which prevents operation of an internal combustion engine in a direction opposite to its normal direction of rotation.

Another object is to provide a method of operating an ignition system whereby the engine is prevented from firing upon rotation of the engine in a predetermined direction.

In accordance with the invention, the ignition system includes a primary circuit comprising a pair of breaker points disposed in series with the primary winding of a magneto coil or of a battery powered ignition coil. Means are provided for grounding the primary circuit upon reverse rotation of the internal combustion engine to prevent firing of the engine.

Other objects, advantages and features will become apparent in the following description and accompanying drawings in which:

FIGURE 1 is a partially schematic, plan view of an ignition system incorporating various of the features of the invention; and

FIGURE 2 is a sectional view taken along line 22 of FIGURE 1.

Referring now to FIGURE 1, the ignition system of the invention is broadly identified by the numeral 10, and generally comprises a primary circuit 12 and a secondary circuit 14. The primary circuit includes a pair of breaker points 16 connected in series with a source of current such as the primary coil or winding 18 of a magneto 20. This invention contemplates the use of a conventional ignition coil and battery and/ or generator arrangement as a source of current in place of the magneto. The primary circuit is grounded at 21 and 23. To reduce arcing and insure instantaneous interruption of the current in the primary circuit, a capacitor 28 is connected across the points 16.

The secondary circuit 14 includes a spark plug 24 connected in series with the secondary coil or winding 26 of the magneto 20. As shown in the drawings, the secondary winding 26 of the magneto 20 is also connected to the ground 27 and the secondary circuit 14 is completed through the ground 21.

The breaker points 16 are carried on a mounting plate 30 in adjacent engaging relationship to each other and comprise a pivotally movable arm or member 32 which is grounded, such as to the mounting plate 30, and a stationary member 34 which is suitably mounted on the mounting plate 30 by a nut 33 and screw 35, referred to as a mounting terminal 36. The stationary member 34 is insulated from the mounting plate 30, but not from the screw 35 and nut 33, by the rubber washer 37 (FIGURE 2) or other suitable insulator means. The primary coil 18 is electrically connected to the mounting terminal 36 so that the terminal 36 is located between the primary coil 18 and the breaker points 16. If desired, the stationary member 34 can be displaced from the mounting terminal and electrically connected thereto through a suitable wire (not shown).

The movable arm 32 is located proximate an ignition c-am shaft 40 extending through a bore 41 in the mounting plate 30 and includes thereon a cam follower member 42 of non-conducting material. The arm 32 is biased toward the shaft 40 by a suitable spring 44 to hold the cam follower 42 in engagement with the ignition cam shaft 40. Though this invention is applicable to a multi-cylinder engine, the illustrated embodiment shows the ignition system 10 adapted for use with a single cylinder engine; therefore, the ignition cam shaft 40 has a single cam lobe The ignition system, thus far described, operates in a conventional manner. Current supplied by the magneto 20 travels through the primary circuit 12. When the cam lobe 50 contacts the follower 42, the breaker points 16 separate to cause a sudden interruption of the current flow in the primary circuit 12 including the primary'coil 18, thereby inducing a high-voltage in the secondary coil 26, which voltage is sufficiently high to cause firing of the spark plug 24. The capacitor 28 absorbs any current which would tend to cause ancin g across the breaker points 16.

Because ignition systems on multi-cylinder twocycle engines (particularly battery ignition systems) can pro duce equally effective spark plug voltages if the engine is operated in an undesired reverse rotation, means operable in response to rotation of the engine in reverse direction are provided to prevent reverse engine operation by preventing the points from interrupting current .flow through the primary circuit 12 and ultimately to prevent the engine from firing.

The aforementioned means is effective to insure continued current flow in the primary circuit 12, when the engine is rotated in the reverse direction, by grounding the primary circuit at a point between the source of current and the breaker points 16. When the primary circuit is thus grounded, the opening and closing of the points 16 cannot interrupt current flow in the primary circuit 12, thereby preventing a high-voltage from being induced in the secondary coil 26 of the magneto 20 and ultimately preventing the engine from starting.

In the preferred embodiment, the aforementioned means generally comprises a grounding spring carried on the ignition cam shaft 40. In the illustrated embodiment, the spring 60 operates in response to reverse rotation of the ignition cam shaft 40 to ground the primary circuit at a point between the primary coil 18 and the breaker points 16. The spring 60 is disposed to contact the extended end 61 of the mounting terminal screw 35 upon reverse rotation of the engine to thereby ground the insulated point 34 and provide an alternate path for the current flow in primary circuit 12 in lieu of a current flow path through the breaker points 16.

More particularly, the spring 60 has a circular portion 62 which snaps into a groove 66 in the ignition cam shaft 40. The spring 60- is resilient, and the circular portion 62 is of slightly less diameter than that of the groove 66 so that the spring 60 tightly grips the ignition cam shaft 40 to provide a ground connection for the spring 60. The spring 60 has an arm or extension 64 which is disposed to move between the insulated contact point 34 and a stop pin 68 extending from the mounting plate 30.

In the illustrated embodiment, normal rotation of the engine affords rotation of the ignition cam shaft 40 in a clockwise direction (as shown by the arrow in FIGURE 1). Under such normal operating conditions, the arm 64 3 of the spring 60 engages the spring stop 68 (as shown in broken lines in FIGURE 1) with no effect on current flow in the primary circuit 12. The pressure of the grounding spring 60 against the stop pin 68 tends to loosen the fit of the spring 60 in the ignition cam groove 66, thus reducing running friction therebetween and allowing easy relative rotation between the ignition cam 40 and the grounding spring 60.

If the engine should attempt to operate in a reverse rotation condition (in a counter-clockwise direction as seen in FIGURE 1), the arm 64 of the grounding spring 60 engages the mounting terminal screw 35 (as shown in phantom lines in FIGURE 1) thereby grounding the ignition primary circuit 12 and thereby preventing firing of the spark plug 24. Under such reverse rotation conditions, the pressure of the grounding spring 60 against the mounting terminal screw 35 tends to tighten the fit of the spring 60 in the ignition cam groove 66, there-by insuring a good ground contact.

Various of the features of the invention are set forth in the following claim.

What is claimed is:

1. An ignition system for an internal combustion engine, said system comprising a mounting plate grounded to the engine, a shaft driven by the engine and including thereon an ignition cam, a mounting terminal electrically insulated from said mounting plate, a pair of breaker points carried on said mounting plate and disposed to be opened and closed by said ignition cam, oneof said points being electrically connected to said mounting terminal, the other of said points being electrically connected to said mounting plate, a magneto having a primary winding with a ground to said engine, said primary winding being electrically connected to said mounting terminal, a stop pin mounted on said mounting plate, and a spring carried on said ignition cam shaft and having an arm disposed to contact said stop pin upon rotation of said engine in a normal operating direction and to contact a portion of said mounting terminal upon rotation of said engine in a reverse direction to afford grounding of said ignition system and thereby prevent engine firing, said spring including a partially circular portion which resiliently grips said ignition cam shaft, said grip of said spring loosening upon contact of said arm with said stop pin and said grip of said spring tightening upon contactof said arm with said mounting terminal.

References Cited UNITED STATES PATENTS 7/1922 Kennington 1'23148 2,881,744 4/1959 Fox 123-4-1 LAURENCE M. GOODRIDGE, Primary Examiner. 

